Reactivity of triruthenium thiophyne and furyne clusters: competitive S-C and P-C bond cleavage reactions and the generation of highly unsymmetrical alkyne ligands

The synthesis and reactivity of the thiophyne and furyne clusters [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, O) is reported. Addition of P(C4H3E)3 to [Ru3(CO)10(mu-dppm)] (1) at room temperature in the presence of Me3NO gives simple substitution products [Ru3(CO)9(mu-dppm)(P(C4H3E)3)] (E = S, 2; E = O, 3). Mild thermolysis in the presence of further Me3NO affords the thiophyne and furyne complexes [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 4; E = O, 6) resulting from both carbon-hydrogen and carbon-phosphorus bond activation. In each the C4H2E (E = S, O) ligand donates 4-electrons to the cluster and the rings are tilted with respect to the mu-dppm and the phosphido-bridged open triruthenium unit. Heating 4 at 80 degrees C leads to the formation of the ring-opened cluster [Ru3(CO)5(mu-CO)(mu-dppm)(mu3-eta3-SC4H3)(mu-P(C4H3S)2)] (5) resulting from carbon-sulfur bond scission and carbon-hydrogen bond formation and containing a ring-opened mu3-eta3-1-thia-1,3-butadiene ligand. In contrast, a similar thermolysis of 3 affords the phosphinidene cluster [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2O)(mu3-P(C4H3O))] (7) resulting from a second phosphorus-carbon bond cleavage and (presumably) elimination of furan. Treatment of 4 and 6 with PPh3 affords the simple phosphine-substituted products [Ru3(CO)6(PPh3)(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 8; E = O, 9). Both thiophyne and furyne clusters 4 and 6 readily react with hydrogen bromide to give [Ru3(CO)6Br(mu-Br)(mu-dppm)(mu3-eta2-eta1-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 10; E = O, 11) containing both terminal and bridging bromides. Here the alkynes bind in a highly unsymmetrical manner with one carbon acting as a bridging alkylidene and the second as a terminally bonded Fisher carbene. As far as we are aware, this binding mode has only previously been noted in ynamine complexes or those with metals in different oxidation states. The crystal structures of seven of these new triruthenium clusters have been carried out, allowing a detailed analysis of the relative orientations of coordinated ligands.     

Essential oil composition of Pimpinella anisum L. fruits from various European countries

Variations in the essential oil composition of Pimpinella anisum L. fruits obtained from different geographical areas of Europe were determined using capillary GC and GC-MS techniques. The essential oil content of the samples was 10.0-53.6 mL kg(-1) and did not confirm to the European Pharmacopoeia standard in 5 samples out of 14. A total of 21 compounds were identified and significant quantitative differences were observed among the samples. The major component was trans-anethole (76.9-93.7%); the other principal compounds in oils were gamma-himachalene (0.4-8.2%), trans-pseudoisoeugenyl 2-methylbutyrate (0.4-6.4%), p-anisaldehyde (tr-5.4%) and methylchavicol (0.5-2.3%). The highest content of trans-anethole (>90%) was found in the samples from Greece, Hungary, Scotland, Lithuania, Italy, and Germany (2 samples). Essential oil of aniseed from Estonia was rich in gamma-himachalene (8.2%) and trans-pseudoisoeugenyl 2-methylbutyrate (6.4%). The sample from France contained the highest amount of anisaldehyde (5.4%) comparing with other samples (0-3.1%). beta-Bourbonene and alpha-farnesene are determined in anise oil for the first time.     

Plasmon enhanced light absorption in bulk heterojunction organic solar cells

Silver nanospheres (Ag NSs) buffer layers were introduced via a solution casting process to enhance the light absorption in poly (3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C61 butyric acid methyl ester (PCBM) bulk heterojunction organic solar cells. These Ag NSs, as surface plasmons, could increase the optical electric field in the photoactive layer whilst simultaneously improving the light scattering. As a result, this buffer layer improves the light absorption of P3HT:PCBM blend and consequently improves the external quantum efficiency (EQE) of organic solar cells. In this work, different sizes of Ag NSs plasmon‐enhanced layer were investigated, with the aim of optimizing the performance of devices. UV‐vis spectrometer measurement demonstrates that the total optical absorption of P3HT:PCBM blend films in the spectral range of 350–650 nm is increased by ～4 and 6% with incorporation of the 20 and 40 nm Ag NSs, respectively. The J_sc was shown to increase by ～21 and 24% for 20 and 40 nm Ag NSs, respectively. This is due to the extra photogenerated excitons by the plasmonic resonance of Ag NSs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An investigation of dielectric resonator antenna produced from silicon (100) enhanced by strontium doped-barium zirconate films

Dip-coated Ba_1−x Sr _x ZrO₃ thick films with different Ba/Sr ratios (x = 0.0, 0.1, 0.3, 0.5, 0.7 and 0.9) were fabricated on Si (100-orient) substrate at a low temperature of 800 °C via the sol gel method. The experimental results show that dielectric resonator (DR) properties of Ba_1−x Sr _x ZrO₃ films depend on the different Ba/Sr ratios. For structural characterization, the X-ray analysis revealed that phase transformation was affected by the increase in Sr concentrations for heat treatment at 800 °C. The films were crystalline and of single phase. The thickness of one BSZ film is around 1.259 μm when measured using the field emission scanning electron microscope. The BSZ film’s surface morphology as indicated by the atomic force microscopy showed the mean grain size to be in the range of 2.56 to 94.34 μm, and the surface roughness (RMS) was recorded to be between 2.35 to 19.64 nm. The dielectric resonator (DR) properties were measured using a network analyzer. By introducing Ba_1−x Sr _x ZrO₃ (BSZ) films on the high dielectric Si (100-orient) substrate, better frequency stability was achieved i.e. within the range of 8–10 GHz. Measured results show that Si (100-orient) DRA has a 10 dB impedance bandwidth of 4.11% at 9.34 GHz and the BSZ improved this to 11.34% with x = 0.7 at 9.15 GHz. The radiation pattern was observed to be stable throughout the operating frequency and holds good potential for DR applications.     

Facile method for the preparation of water dispersible graphene using sulfonated poly(ether-ether-ketone) and its application as energy storage materials

A simple and effective method for the preparation of water dispersible graphene using sulfonated poly(ether-ether-ketone) (SPEEK) has been described. The SPEEK macromolecules are noncovalently adsorbed on the surface of graphene through π-π interactions. The SPEEK-modified graphene (SPG) forms an aqueous dispersion that is stable for more than six months. An analysis of the ultraviolet-visible spectra shows that the aqueous dispersion of SPG obeys Beer's law and the molar extinction coefficient has been found to be 149.03 mL mg(-1) cm(-1). Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy analyses confirm successful reduction and surface modification of graphene. An atomic force microscopy (AFM) analysis reveals the formation of a single layer of functionalized graphene. Transmission electron microscopy results are also in good agreement with the AFM analysis and support the formation of single-layer graphene. SPG shows good electrochemical cyclic stability during cyclic voltammetry and charge/discharge process when used as a supercapacitor electrode. A specific capacitance of 476 F g(-1) at a current density of 6.6 A g(-1) is observed for SPG materials.     

Titanium(IV) Complexes of Unsymmetrical Schiff Bases Derived from Ethylenediamine and o‐Hydroxyaldehyde/Ketone and Their Anti‐microbial Evaluation

The titanium(IV) complexes of the unsymmetrical Schiff base ligands (L) of ethylenediamine and salicylaldehyde, o‐hydroxyacetophenone, o‐hydroxynapthaldehyde have been prepared and characterized when unsymmetrical ligands are synthesized through in situ partial displacement of the symmetrical bis‐Schiff bases. Compounds have been characterized by elemental analysis, electronic, (Infra‐red) IR, 1H NMR spectral data, magnetic susceptibility measurement and molar conductance and eight coordinated geometry of the complexes was proposed. The complexes have been found to posses 1:2:1 (M:L:B) stoichiometry (B is the secondary ligand). The bio‐efficacy of the prepared complexes has been examined against the growth of bacteria and fungi in vitro to evaluate their anti‐microbial potential.     

Phytochemical analysis of the essential oil of Achillea millefolium L. from various European Countries

Variations in the essential oil composition of Achillea millefolium L. growing in Estonia and in other European countries, were determined. The oils were obtained in yields of 0.9-9.5 mL kg-1. A total of 102 components were identified. The quantitatively most important components of yarrow were sabinene, beta-pinene, 1,8-cineole, artemisia ketone, linalool, alpha-thujone, beta-thujone, camphor, borneol, fenchyl acetate, bornyl acetate, (E)-beta-caryophyllene, germacrene D, caryophyllene oxide, beta-bisabolol, delta-cadinol, chamazulene etc. Samples from Estonia contained high amounts of monoterpenes and chamazulene. High amounts of monoterpenes and chamazulene were also found in samples from Hungary, Greek, Moldavia, Latvia, Lithuania and Germany. The oils from France, Belgium, Russia, Armenia, Spain and Italy were rich in oxygenated monoterpenes and contained a little amount of chamazulene. The drugs from Greece, Estonia, Moldavia and Scotland were rich in sesquiterpenes. The Millefolii herba grown in Estonia conforms to the European Pharmacopoeia (EP) standards in the aspect of the essential oil contents.     

Screened exchange hybrid density-functional study of the work function of pristine and doped single-walled carbon nanotubes

We present a detailed study of the work function of pristine and doped single-walled carbon nanotubes (SWCNTs) using a novel screened exchange hybrid density functional. We find that SWCNTs with diameters larger than 0.9 nm tend asymptotically and smoothly to the graphene limit of 4.6 eV. On the other hand, the work function of narrow tubes exhibits a strong dependence on their diameter and chiral angle. Boron or nitrogen doping, with concentrations from 1% to 2%, not only changes the electronic behavior by introducing new states around the Fermi level, but also produces a significant change of the work function that can vary between 3.9 (N doping) and 5.2 eV (B doping).     

Characterization of catechol 1,2-dioxygenase from cell extracts of <Emphasis Type="Italic">Sphingomonas xenophaga</Emphasis> QYY

Sphingomonas xenophaga QYY, capable of growing significantly on more than ten kinds of aromatic compounds as sole carbon source, was used to study characterization of catechol 1,2-dioxygenase (C12O) in cell extracts. Characterization of the crude C12O showed that the maximum activity was obtained at 40–70°C and pH 7.8–8.8. Metal ions had different influences on the activity of crude C12O. It was suggested that strain QYY possessed an inducible and ferric-dependent C12O. Kinetic studies showed that the value of V _max and K _m was 0.25 μmol catechol/L/mg protein/min and 52.85 μmol/L, respectively. In addition, the partial purification of C12O was achieved by a HiTrap Q Sepharose column chromatography. Supported by the National Natural Science Foundation of China (Grant No. 50608011) and the 39th Postdoctoral Funds of China (Grant No. 20060390983)     

Space complexity of Abelian groups

We develop a theory of LOGSPACE structures and apply it to construct a number of examples of Abelian Groups which have LOGSPACE presentations. We show that all computable torsion Abelian groups have LOGSPACE presentations and we show that the groups , and the additive group of the rationals have LOGSPACE presentations over a standard universe such as the tally representation and the binary representation of the natural numbers. We also study the effective categoricity of such groups. For example, we give conditions are given under which two isomorphic LOGSPACE structures will have a linear space isomorphism.